Acetaminophen
Acetaminophen (paracetamol) is a synthetic non-opiate analgesic and antipyretic. **Clinical Pearls & Veterinary Context:** * **Extremely toxic to cats and ferrets** at any dose due to their deficiency in the enzyme glucuronyl transferase, leading to the accumulation of the toxic metabolite NAPQI. * Occasionally used in dogs and small mammals for mild to moderate pain, particularly when NSAIDs are contraindicated (e.g., renal dysfunction). * Lacks significant peripheral anti-inflammatory activity and does not inhibit platelet function at clinical doses. * Often formulated in combination with opioids (e.g., codeine, hydrocodone) for synergistic analgesia.
Mecanismo: Produces analgesia and antipyresis via weak, reversible, isoform-nonspecific inhibition of **cyclooxygenase (COX-3 / COX-1-v1)** in the central nervous system. **Mechanism Pathway:** Inhibition of central **COX** enzymes → decreased **prostaglandin** synthesis in the CNS → elevation of the pain threshold and alteration of the hypothalamic thermoregulatory center → analgesia and antipyresis. *Note: It lacks significant peripheral COX-1 or COX-2 inhibition, which explains its lack of anti-inflammatory and anti-platelet effects.*
Dosificación por especie
- Analgesic (Rabbits) · 1-2 mg/mL in drinking water · PO · Ad libitum · Using Children's Tylenol. Effective for controlling low-grade nociception.
- Analgesic (Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas) · 1-2 mg/mL in drinking water · PO · Ad libitum
- Analgesic · 15 mg/kg PO q8h · PO · q8h
- Analgesic · 10 mg/kg PO q12h · PO · q12h
- Analgesic · 10-15 mg/kg PO q12h · PO · q12h · 5 days
- Treatment of degenerative myelopathy (in German Shepherds) · 5 mg/kg PO (not to exceed 20 mg/kg per day) · PO · Daily
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Cats (at any dosage)
- Ferrets
- Sugar Gliders
- Hedgehogs
Efectos adversos
- Methemoglobinemia (especially in cats and dogs at high doses)
- Hepatotoxicity (liver necrosis)
- Renal effects
- Gastrointestinal disturbances
- Facial and paw swelling (edema)
- Keratoconjunctivitis sicca (KCS)
- Cyanosis
- Hypothermia
Interacciones farmacológicas
- Other Analgesics · Chronic use with acetaminophen may lead to renal pathologies
- Barbiturates · Increased conversion of acetaminophen to hepatotoxic metabolites; potentially increased risk for hepatotoxicity
- Doxorubicin · May deplete hepatic glutathione, thereby leading to increased hepatic toxicity
- Halothane · Not recommended for postoperative analgesia in animals that received halothane anesthesia
- Isoniazid · Possible increased risk of hepatotoxicity
- Phenothiazines · Possible increased risk for hypothermia
- Propylene Glycol · May increase the severity of acetaminophen-induced methemoglobinemia or Heinz body formation
- Warfarin · Large doses may potentiate anticoagulant effects
Monitorización
- Liver enzymes (ALT, AST, ALP)
- Renal function (BUN, Creatinine)
- Hematologic parameters (CBC for methemoglobinemia or Heinz bodies)
- Clinical signs of toxicity (edema, cyanosis, lethargy)
Sobredosis
**Acute Toxicity & Overdose:** * **Clinical Signs:** Methemoglobinemia (brown blood/mucous membranes), liver necrosis, renal effects, facial and paw swelling, keratoconjunctivitis sicca (KCS), vomiting, lethargy, cyanosis, hypothermia. * **Species Differences:** Liver effects are more common in dogs; facial/paw swelling and methemoglobinemia are more common in cats. * **Treatment:** Standard gut emptying techniques (emesis/lavage) and activated charcoal if recent. Administer **acetylcysteine (NAC)** as a glutathione precursor to bind toxic metabolites. Supportive care includes **s-adenosyl methionine (SAMe)**, oxygen therapy, IV fluids, and blood transfusions or methylene blue for severe methemoglobinemia.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.